PROJECT SUMMARY Arrhythmia is a life-threatening condition that impacts the quality of life of millions of patients, and the number of arrhythmia patients is expected to increase in the aging population. For over 50 years, cardiac pacemakers have been implanted into patients' hearts to deliver electrical stimuli to induce the heart contractions at the desired rate. Electrical pacemakers underwent dramatic improvements over the years, but some of their inherent properties related to the electrical nature of their modus of operandi will always create problems that cannot be overcome by further improvements. Among these problems are tissue scarring due to electrochemical processes at the electrode-tissue interface, and the incompatibility with the long list of medical procedures, airport security equipment, and some home appliances. Our project aims to develop an alternative cardiac pacemaker using optical rather than electrical stimulation. This device will be aided by a novel graphene-mediated optical stimulation technology that relies on unique optoelectronic properties of graphene to convert light into electricity and induce the changes in the electrical field across the cardiac cell membrane. This technology combined with an implantable wireless miniaturized LED system is expected to lay the foundation for the new generation of cardiac pacemakers. This feasibility project represents a medium risk / high reward study offering a revolutionary nanotechnology-driven bioengineering solution that is expected to significantly improve existing medical devices for correcting the abnormal heart rhythm. This approach could also be extended beyond cardiology.